Headbox for twin wire paper machine



June 1969 M. s. GREEN HEADBOX FOR TWIN WIRE PAPER MACHINE Filed Feb; 19. 19 65 INVENTOR.

MARSHALL S. GREEN W ATTORNEYS United States Patent 3,450,596 HEADBOX FOR TWIN WIRE PAPER MACHINE Marshall S. Green, Watertown, N.Y., assignor to The Black Clawson Company, Hamilton, Ohio, 21 corporation of Ohio Filed Feb. 19, 1965, Ser. No. 434,051 Int. Cl. D21f N50 US. Cl. 162-338 14 Claims ABSTRACT OF THE DISCLOSURE This invention relates to paper making machinery.

The invention has special relation to paper machinery generally of the type shown in Baxter United States Patent No. Re. 25,333 and characterized by the incorporation of a pair of forming webs arranged to travel vertically in closely spaced relation defining the forming zone wherein formation of the paper sheet takes place. The objects of the present invention relate to a headbox particularly designed for operation with a paper machine of this general type which offers improved features of structure and operation.

It is a primary object of the present invention to provide a headbox for a paper machine as outlined above which has its discharge slot arranged generally vertically at one end thereof and multiple inlets connected along opposite walls thereof across the width of the paper machine and arranged to deliver multiple opposed flows of stock into the interior of the headbox in directions extending substantially normal to the direction of discharge from the headbox to the forming zone.

An additional object of the invention is to provide a headbox as outlined above which incorporates a baflle located centrally thereof in such manner as to block directly horizontal flow of stock from any of the stock inlets to the opposite side wall of the headbox, but with this baflle terminating at a level sufliciently spaced from the discharge slot from the headbox for free mixing of the stock from all of the inlets prior to flow thereof into the forming zone.

Another object of the invention is to provide a headbox for a paper machine as outlined above which incorporates a novel sealing arrangement for maintaining sealing engagement between the end walls of the headbox and the adjacent portions of the forming webs, both in the portions of the forming webs running on the breast rolls and also on the portions depending from the breast rolls through the forming nip.

An additional object is to provide a headbox as outlined in the preceding paragraph incorporating a novel structural arrangement in combination with the seals for the side edges of the forming nip for the purpose of adjusting such seals for optimum forming conditions for the paper sheet.

It is a specific object of the invention to provide a headbox having some or all of the structural and operational characteristics outlined above which may be used as an open headbox under atmospheric pressure or as a closed headbox wherein a cushion of gas is maintained above the level of stock to vary theeffective dischargre pressure with respect to atmospheric pressure.

Patented June 17, 1969 Additional objects and advantages of the invention will be apparent from the following description, the accom- .panying drawing and the appended claims.

In the drawing- FIG. 1 is a diagrammatic view generally in side elevation illustrating a vertical paper machine incorporating an open headbox in accordance with the invention;

FIG. 2 is a somewhat diagrammatic view in vertical section throuhg the headbox and a fragment of the breast rolls in the paper machine of FIG. 1;

FIG. 3 is a fragmentary view partly in section on the line 3-3 of FIG. 2;

FIG. 4 is a fragmentary view in side elevation and on a larger scale of the outer end wall section of the headbox of FIG. 2;

FIG. 5 is a fragmentary view looking from right to left in FIG. 4 and partly in section on the line 55 of FIG. 4; and

FIG. 6 is a view similar to FIG. 2 showing a closed or pressure type headbox in accordance with the invention.

Referring to the drawing, which illustrates preferred embodiments of the invention, the paper making machine of FIG. 1 is shown as generally of the type disclosed in Baxter Patent Re. 25,333. The headbox 10 delivers stock to the space above the nip 11 of a pair of two breast or metering rolls 12 and 13. The couch rolls 14 and 15 are respectively positioned in parallel relationship below the breast rolls 12 and 13, and each pair of breast and couch rolls has a forming wire 16 and 17 entrained therearound so that a vertical forming zone 20 is defined between the breast and couch rolls.

The wires or other forming webs 16 and 17 move downwardly from the nip 11 through the forming zone 20 past the baffles 21 in a gradually converging path guided by the supporting deflectors 22 which exert a squeezing action on the stock between the wires which expels the white water therefrom through the wires, thus forming a paper web. The baflles 21 act as forming boards to minimize suction through the forming wires in the areas closely below the nip 11, and the deflectors 22 also serve the important purpose of removing this water from the rear side of the wires 16 and 17 by deflecting it outwardly and downwardly therefrom into the collection pans 23 and 24 from where it is returned to the white water supply system. As the wires 16 and 17 leave the last pair of deflectors 22, the suction box 25 holds the newly for-med web on the left-hand wire 16 and separates it from the wire 17. The suction box 27 in the couch roll 14 holds the web thereon until engagement with the transfer roll 30, which has a suction box 31 therein for transferring the web from the forming wire 16 to the press felt 33.

The stock supply system is shown fragmentarily in FIG. 1 as including the main stock supply line 35 which is fed by the usual pump or pumps 36 from the usual supply lines or chests, not shown, of fresh stock and white water. The main pipe 35 is connected with multiple lines 40 which lead to the headbox 10', as now described.

The headbox 10 is shown as relatively narrow in proportion to the diameters of the rolls 1215, but this has been done for convenience of illustration, and it is to be understood that the headbox will in every case be proportioned to extend across the full width of the paper machine on which it is used. The head-box 10 comprises a rectangular flow box having opposed side walls 4445 and end walls 46 and 47. The discharge slot 50 through which the stock is delivered to the forming nip 11 is defined by side wall edge portions 52 and 53 which converge downwardly at equal angles from the main side walls 44-45 to locate the slot 50 substantially centrally of the bottom of the headbox 10. The side Wall portions 52 and 53 are shown as parts of the main side walls 44-45, but they may if desired be pivotally connected to walls 44-45 for relative adjustment to vary the width of slot 50, as described in copending application Ser. No. 253,858 filed Jan. 25, 1963, now Patent No. 3,215, 593.

In accordance with the invention, the stock is delivered to the interior of the headbox by multiple inlets 55 which are arranged in uniformly spaced relation across the full extent of the side walls 44 and 45 above their edge portions 52-53. More specifically, each of these inlets 55 is formed by a short length 56 of pipe secured in substantially perpendicular relation to the associated side wall 44 or 45, and the inlets 55 preferably are located directly opposite each other and define a plane normal to the direction of discharge of stock through the slot 50. For optimum results, provision should be made to deliver stock to all of the inlets 55 under essentially equal velocity and pressure conditions, as by means of lines 40 of essentially equal length and diameter and fiow distributing means such as are shown in application Ser. No. 323,533, now Patent No. 3,296,066.

The arrangement of the inlets 55 as described in equally spaced opposed relation along the side walls 44 and 45 of the headbox is believed to contribute to the desired uniformly high quality of sheet formation on the paper machine. Apparently the entering flows from opposed pairs of inlets 55 generate a high intensity of turbulence for defiocculation of the fibers and thorough intermixing of the fibers in the desired uniform distribution throughout the remainder of their passage to the forming zone 20 of the paper machine. For preferred results, however, the headbox is equipped with a partition 58 located substantially equidistant from the side walls 44-45 and extending from a level sufliciently above the inlets '55 to a level sufficiently below these inlets to block directly horizontal flow of stock from one side wall to the other, thereby preventing oscillation of the stock in the headbox. The partition 58, however, terminates along its lower edge at a level sufliciently above the discharge slot 50 for free mixing of the stock from all the inlets 55 prior to flow thereof through the slot.

The construction of the end walls of the end box, particularly the portions which are adjacent the ends of the nip 11 and the upper portion of the forming zone 20, is of special importance in achieving the principles of the invention. Referring to FIGS. 4-5, an end plate 60 is secured as by screws 61 to the tapered lower end portion of the end wall 47, and it will be understood that this construction is duplicated at the end wall 46. The lower side edges 62 and 63 of the plate 60 are curved substantially concentrically with the respective breast rolls 12 and 13, and the plate 60 also includes an elongated finger portion 65 which depends through the nip 11 generally tangent to the curved edges 62-63 and terminates in a tapered point 66.

The bottom portion of the end wall 47 terminates above the actual nip 11, and it is provided on its inner surface wih a wedge-shaped member 70 which abuts the walls 52-53 and has its inner surface 71 inclined inwardly and downwardly. Since there is a complementary wedge member on the opposite wall 46, it will be seen that their surfaces cooperate to cause slight convergence of the downward flow of stock into the nip, which will minimize the otherwise likely tendency of the stock to spread outwardly as it enters the nip. The wedge 70 could readily be integral with the wall 47, and it is shown as having an integral depending portion with a vertical inner surface 72 aligned with the lower end of the inclined surface 71. This portion substantially fills in the space below the wall 47 and between the two breast rolls, and the same results may be obtained by means of a similarly shaped portion of the wall 47 or plate 60 or by a separate piece directly supported on the Wall 47 or the plate 60.

The plate 60 is provided with seal members for maintaining running sealing engagement with the forming wires both against the portions of the breast roll approaching the nip and also through and below the nip in the areas bounded by the baflles 21. These seal members comprise strips of resilient or otherwise flexible foam material 75 directly secured to the side edges of the plate 60 and finger portion 65, and each of these strips is provided with a facing layer 77 of material which will form an effective running seal against one of the forming wires. For example, satisfactory results have been obtained with the strips 75 formed of a closed cell sponge neoprene .25 inch thick and provided with a layer 77 of polyurethane approximately .060 inch in thickness.

The sealing strips are shown as anchored on top of the plate 60 by clamp screws 76, and the strip 75 is glued by a suitable water resistant adhesive both to the edges of the plate 60 and the finger portion 65 and to the facing layer 77. It is desirable to provide for some adjustment of the plate 60 and its sealing strips in order to assure proper sealing with minimum unnecessary friction against the forming wires. These results can be obtained by locating the mounting screws 61 in slots 78 in the plate 60, which makes it possible to let the plate 60 settle into proper position with respect to the breast rolls and then to lock it into that position by tightening the screws 61.

The two sealing strips converge towards each other along the sides of the tip portion 66 of the finger 65 and their portions which depend below the finger and between the baffles 21 are adhered directly together. This depending portion identified at 80 is adjustable as indicated in FIG. 5 laterally of the forming wires, by means of an adjusting screw 81 mounted in any convenient bracket portion 82 of the main frame of the machine. This tip adjustment provides a final accurate control of the edge portions of the stock flow between the wires just as it flows beyond the batlles or forming boards 21, minimizing immediate edge leakage and imparting correspondingly improved edge characteristics to the sheet.

It will be apparent that the headbox and associated parts are shown diagrammatically for convenience of illustration, and it should be understood that all these parts are to be appropriately proportioned in accordance with the principles of the invention for all sizes of paper machines. For example, highly satisfactory test results have been obtained with a paper machine and stock supply system constructed as described and built with rolls 12- 13 each 30 inches in diameter at operating speeds as high as 3000 feet per minute with a headbox constructed as disclosed and provided with inlets 55 each 2 inches in diameter and spaced on 3-inch centers.

While the invention has been described in connection with an open headbox 10, it is equally applicable to a closed headbox of the air loaded type, and such pressure headbox is preferred for higher operating speeds, particularly above 1800 feet per minute. FIG. 6 shows a pressure headbox which is in many respects of essentially the same construction as the headbox 10, and to the extent to which they are applicable, corresponding reference characters 44, 45' and so forth have been used therein.

The headbox 100 differs from the headbox 10 primarily in the provision of a top wall 101 which encloses the interior of the headbox and is provided with a connecting pipe 102 to a suitable source of a positive or negative gas pressure. When this headbox is operated with superatmospheric pressure in the space above the liquid level, it is necessary to provide means for preventing this pressure from causing the liquid level in the nip 11' to overflow the breast rolls. For this purpose, flexible sealing strips 105 and 106 are secured along the lower edges of the walls 52' and 53' in such manner as to be held in sealing engagement with the forming wires 16' and 17 by the pressure of the stock in the headbox. Accordingly, these seal strips 105 and 106 should be made of flexible material which will provide sealing engagement against the wires with minimum friction, and rubber may be used for this purpose or a material like that used for the sealing strips 77.

The internal construction of the headbox 100 may be identical with that of the headbox with a single exception. Provision must be made for direct communication between the spaces on the two sides of the partition 108, and it is accordingly provided with one or more through holes 109 for equalizing the liquid level and gas pressure on the two sides thereof. Otherwise, the construction and operation of this form of the invention may be essentially the same as already described in connection with FIGS. 1-5.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A headbox for delivering paper making stock to a paper machine having a pair of breast rolls arranged in horizontally spaced relation defining a vertically extending nip therebetween and a pair of forming webs arranged for travel around said breast rolls and downwardly through said nip in spaced relation defining a forming zone therebetween, comprising a flow box having a pair of opposed side walls proportioned to extend the full width of the paper machine above said forming zone, a pair of end walls secured to said side walls, said flow box including an additional pair of walls depending from said side walls and converging to define with said end walls a tapered discharge passage having a discharge slot at the lower end thereof for discharging stock downwardly into said forming zone, a pair of end plates secured to said end walls to close the ends of said passage, said end plates being contoured to extend into and through said nip and having edge portions overlying said breast rolls, and seal means on said edges of said end plates adapted for running sealing engagement with said forming'webs against the faces of said breast rolls and through said nip to limit the flow of stock from said nip axially of said breast rolls.

2. A headbox as defined in claim 1 comprising wedge portions on the inner surface of each of said end walls and between said additional walls, said wedge portions being arranged to slope downwardly and inwardly of said headbox to cause corresponding convergence of the flow of stock through said slot.

3. A headbox as defined in claim 1 wherein each of said and plates has side edges curved substantially concentrically with the adjacent said breast roll, and said seal means includes a strip of flexible material extending along each said curved edge of said end plate and engaging the adjacent said forming web.

4. A headbox as defined in claim 1 wherein each of said end plates has side edges curved substantially concentrically with the adjacent said breast roll and also includes an elongated finger portion depending through said nip, said seal means including a strip of flexible material extending along each said curved edge of each of said end plates and said finger portions thereof for engagement with the adjacent said forming web, and said seal strips including end sections depending below said finger portions.

5. A headbox as defined in claim 4 comprising means for eifecting adjusting movement of said depending end sections of said seal strips laterally of said forming webs.

6. A headbox as defined in claim 2 wherein each of said end plates has side edges curved substantially concentrically with the adjacent said breast roll and also includes an elongated finger portion depending through said nip, said seal means including a strip of flexible material extending along each said curved edge of each of said end plates and said finger portions therefor engagement with the adjacent said forming web, said seal strips including end sections depending below said finger portions, and means for effecting adjusting movement of said depending end sections of said seal strips laterally of said forming webs.

7. A headbox as defined in claim 1 comprising a top wall for enclosing a cushion of gas above the level of stock in said box, and a flexible sealing strip secured along the lowermost edge of each of said additional walls and depending therefrom into running sealing engagement with the adjacent said breast roll to prevent flow of stock from said headbox except through said nip.

8. A headbox as defined in claim 1 comprising a bafiie member located below said nip between each said breast roll and the associated forming web for minimizing suction through said Webs in the areas closely below said nip, each of said end plates having side edges curved substantially concentrically with the adjacent said breast roll and also including an elongated finger portion depending through said nip between said baflie members, and said seal means including a strip of flexible material extending along each said curved edge of each of said end plates and said finger portions thereof for engagement with the aidjacent said forming web against the adjacent said breast roll and baflie member.

9. A headbox as defined in claim 8 wherein said seal strips include end sections depending below said finger portions between said bafile members, and means for effecting adjusting movement of said depending end sections of said seal strips laterally of said forming webs.

10. A headbox for delivering paper making stock to a paper machine having a pair of forming webs arranged for downward travel in spaced relation defining a forming zone therebetween, comprising a flow box having a pair of opposed side walls proportioned to extend the full width of the paper machine above said forming zone, said flow box including an additional pair of walls depending from one of said side walls to the other, said partition discharge passage having a discharge slot at the lower end thereof for discharging stock downwardly into said storming zone, and means defining a plurality of inlets in each of said side walls arranged in horizontally spaced relation to deliver stock to the interior of said box in a corresponding plurality of horizontal flows from opposite sides of said box for intermixing and flow to said discharge slot.

11; A headbox as defined in claim 10 comprising means forming a partition located substantially equidistant from said side walls and extending from a level below the lowermost of said inlets to a level above the uppermost of said inlets to block directly horizontal flow of stock from one of said side walls to the other, said partition terminating at a level sufiiciently above said discharge slot for free mixing of the stock from all of said inlets prior to flow thereof through said slot.

12. A headbox as defined in claim 10 wherein all of said inlets are arranged in horizontally aligned relation, and the total flow area of said inlets in one of said side walls is substantially equal to the total flow area through said inlets in the other of said side walls.

13. A head-box as defined in claim 10 having a top wall located at a level substantially higher than the highest of said inlets for enclosing a cushion of gas above the level of stock in said 'box.

14. A headbox as defined in claim 13 comprising means forming a partition located substantially equidistant from 7 8 said side walls and extending from a level below the References Cited lowermost of said inlets to a level above the uppermost of UNITED STATES PATENTS said inlets to block directly horizontal flow of stock from one of said side walls to the other, said partition terminating at a level sufficiently above said discharge slot 5 for free mixing of the stock from all of said inlets prior to flow thereof through said slot, and means forming a LEON BASHORE Prlmary Exammer' communicating passage from one side of said partition to U S Cl X R the other above the level of the uppermost of said inlets l for equalizing the pressures on the two sides of said bafiie. 10 301, 203

2,969, ll4 1/1961 Baxter 162203 X 3,296,066 1/1967 Green et a1. 162338 mg? UNITED STATES PATENT ()FFICE CERTIFICATE OF CORRECTION Patent No. 59 Dated June 9 9 lnve mfl I Marshall S. Green It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 54 "and plates" should read end plates--. Column 6, line 5, "therefor engagement" should read thereof for engagement line 43 should read as follows from said side walls and converging to define a tapered SIGNED ANu SEALED NW4 m (SEAI) Attest:

Au i Offi mmissionerof Patents 

